The present invention relates to novel paranitroaniline derivatives usable in non-linear optics and in electrooptics, as well as to the preparation process for the same.
The term non-linear optics is understood to mean the field of optics extending from the conversion of optical frequencies (obtaining an optical radiation from two radiations of different frequencies, the frequency of the conversion radiation being equal to the sum or the difference of the frequencies of the two radiations) to electrooptical modulation (modification of one of the characteristics of a radiation by applying an electrical field to a crystal traversed by said radiation).
Numerous materials which are suitable for converting optical frequencies or for electrooptical modulation are already known. The most widely used are frequency doubling crystals based on potassium diphosphate KDP or lithium niobate.
However, these mineral materials have the disadvantage of inadequate efficiency, which makes it necessary to use them in considerable thicknesses. In addition, for a number of years research has been directed at producing crystals of organic molecules having an improved efficiency compared with mineral crystals of potassium diphosphate or lithium niobate. Thus, it has been found that aniline derivatives such as metanitroaniline, 2-methyl-4-nitroaniline, 2-chloro-4-nitroaniline, 2-bromo-4-nitroaniline and methyl-2(2,4-dinitrophenyl)-aminopropionate can be used for this purpose. It has also been found that pyridine-N-oxide derivatives have interesting properties, one example being 3-methyl-4-nitropyridine-1-oxide (cf "A molecular engineering approach toward the design of efficient organic crystals for three-wave mixing" J. Zyss in Current Trends in Optics, p. 122 (Taylor and Francis, London 1981); B. L. Davydov et al ZhETF Pis. Red, 12(1), 24 (1970); and B. F. Levine, C. G. Bethea, C. D. Thurmond, R. T. Lynch and L. Bernstein, J. Appl. Phys. 50, 2523, 1979.